1. Field
The present invention relates to a power steering apparatus.
2. Related Art
For an electric power steering apparatuses for vehicles, during assembly, setting an inter-axis distance between a worm gear and worm wheel needs to be easily performed without being affected by a dimensional error in components such as the worm gear. After assembly, even if the meshing between the worm gear and the worm wheel is subjected to a temporal change, the inter-axis distance needs to be easily adjusted to eliminate backlash in the worm gear and the worm wheel.
For example, JP-5859891-B discloses an electric power steering apparatus having a preload unit that biases a bearing that supports a tip shaft portion of the worm gear, in a predetermined preload direction, so as to impose a preload on the meshing portion between the worm gear and the worm wheel. Japanese JP-5859891-B further discloses that the bias force exerted by the preload unit is used to adjust the inter-axis distance between the worm gear and the worm wheel to eliminate backlash in the worm gear and the worm wheel.
In the configuration in which the preload is imposed on the meshing portion between the worm gear and the worm wheel, a meshing reaction force exerted between the worm gear and the worm wheel may cause the bearing to slide in the preload direction and in a direction opposite to the preload direction. In such a case, sliding of the bearing is expected to lead to lack of a lubricant such as grease, hindering, for example, smooth sliding of the bearing.